Monolithic flat slab



K. R. SCHUSTER.

NIONOLIT'HIC FLAT SLAB.

APPLxcATloN FILED luNE l. |918.

Patented May 30, 1922.

2 SHEETS-SHEET I.

IVM) E K. R. SCHUSTER.

IVIONOLITHIC FLAT SLAB.

APPLICATION FILED IUNE I, I9I8.

Patented May 30, 1922.

2 SHEETS-SHEET 2.

Z |NvENToR zsmm ATTORNEY UNITED STATES PATENT oFFicE.

KARL 12,.v SCHUSTER, 0F BROKLYN, NEW YORK.

MONOLITHIC man SLAB.

Specication of Letters Patent. l Patented May 30, 1922.V

Application led June 1, 1918. Serial No. 237,700.

` ordinary floor constructionsof a composite nature. v

lt is well known to construction en meers that composite fiat slabs supported so ely by4 columns are subjected to load stresses diifering widely in character from the stresses incurred in composite plates the margins of which are supported by walls and beams.

ln the present invention, the fiat slab is i'ree from the support aiforded by beams and girders. finding its support through the medium of columns the couples of which are spaced equi-distantly apart, for which reason l stitfen the slab by a reinforce known in the art as a two-way reinforce, the same comprising` two belt courses of rods or bars --located below the neutral axis of the slab and in the tension chord thereof. the rods of one belt course crossing at a right angle the rods of the other belt course, andthe two courses of rods running diagonally to the center lines between and through'the columns.

The composite flat slab is reinforced substantially equally in bothv directions by the belt courses of rods, the saine affording a simple construction economical in the use of steel, but experience shows that a twoway reinforced slab of the character under consideration when supported by columns coupled in pairs spaced equi-distantly is subjected. to greater stresses along the lines of the diagonals between opposite couples of, the adjoining pairs of columns, for the reason that the distance is greateru on the diagonale between opposite couples of the adjacent pairs of columns than it is between the columns composing the couples or pairs.

Accordingly. this invention embodies a distribution oi the steel or of the materials entering into the construction of the slab in such a nianner as to take care of the diagonal stresses in a two-way reinforced slab. This object 1s attained by using steel in greater quantity .along the diagonals, or the same endmay be attained by the use of an increased volume of masonry for of stronger masonry, or anyl combination of the steel and masonry, to thereby take care of those parts of the fiat slab which are subjected to the greater stresses. i

In a two-way reinforced flat plate-or slab the use of two crossing belt courses of rods each utilizing the same 'amount of steel, it is apparent that the resulting slab'is theoretl ically equally strong in tension in any direction.v Such lreinforced slab is rthus well adapted for resisting load stresses when distributed equally, but the use of a slab in connection with columns the couples of which are spaced equally develops areas or strips of material which are weaker along the lines of. the diagonale between the col` umns than'strips or areas along the center lines between said columns. To secure the necessary stability along the diagonal areas the quantity of material is increased to a substantial extent along the areas extending' diagonally between the columns.

Other functions and advantages of the invention will appear from the following description taken in connection with the drawings, the latter illustratinoseveral embodiments of the invention, wherein- Fig. 1 is a plan view illustrating a monolithic flat slab embodying this invention, the` dotted lines illustrating in part the equidistant spacing of the columns coupled in pairs, and certain lines indicating the margins of the slab extending through the center line of the columns.

Fig. 2 is a plan view of another embodiment of the invention illustrating a, sin le column and the means for'reinforcing 'ie slab associated with said column.

Fig. 3 is a plan View of another embodiment of the invention illustrating another 100 -form of reinforce.

Figs. 4 and 5 are' vertical sections in the planes of the dotted lines 4-4 and 55, respectively, of Figs. 2 and 3.

Fig. 6 is a plan view illustrating another 105 one column of a pair or couple to the oppo- 110 site column of an adjoining pair or couple to show the means for increasing the strength of the slab onthe diagonal line between the specified columns.

Figs. Sand 9 are plan views of other embodiments of the invention wherein the rods or bars are positioned in the slab to the a result of which organization and relation the slab under load stresses simulates the action of a fiat plate.

As shown by the lines extending between the columns in Fig. 1, the couple or pair of columns D E are spaced equidistantly from the adjacent couple or-pair F, Cr, but the distance between the center of columns D G or E F being on the diagonals, exceeds the distance between anyl two columns composing a couple or pair. y

The rods B constitute a belt course extending throughout the area of the slab, whereas the other rods C form a second belt course also extending `throughout the area of the slab. Said rods IBl C are of equal cross section individually, and they are embedded in the material of the slab below the neutral axis and Ain the tension chord thereof.-

All the rods are arranged diagonally to the lines extending centrally through the col-- umns so as to cross the lines indicating said center lines, and thus the diagonal rods are continuous through a panel supported by four columns so as to extend -beyond the marginsofsaid panel and into the panels adjacent to the panel bounded bythe four center lines.

The rods B of one belt course cross or intersect with the rods C of the other belt course, and yall said rods are spaced equidistantly, which relation of the rods provides spaces adapted for the reception of hollow tiles as disclosed in my prior Patent No. 1,134,164, although it is to be understood that the slab may be composed solely of concrete reinforced in accordance with this invention.

The slab reinforced by the crossing belt courses of rods embodies a construction wherein the areas extending parallel to the central lines between the columns are reinforced to carry the load stresses without fracture, but experience shows that tle weakest areas of such a reinforced slab are on the diagonal lines betweenthe couples of equiof rods B3 distantly s aced columns; Accordingly, in

this inventlonI dispose or organize the steel to take care of the greater stresses developed on the longer diagonal lines betweendshe columns, and to this end I employ either of the severall constructions depicted in the draw-` Iii Fi 1,l the rodsB C extending on the diagona s are of increased cross section or much heavier than the rods B C in the two intersecting belt courses of rods comprising in part the two-way reinforcement. Thus there is a group of heavier rods B extending between the columns D G, and another group of heavier rods C extending between the columns E, F, the rods B, C being in the lower chord of the slab and parallel to the rods B C respectively, said heavier rods B- C constituting a part of the reinforcement the remainder of which is afforded by the lighter rods B C.

All the rods run diagonally through the l The mat or grill is positioned in the upper chord ofthe slab, and the area of the mat or grill exceeds' the cross section of the column, whereby said mat or grill operates to take care of the negative bending moment i and of the vertical shear'present in the slab at the areas adjacent the column.

' The slab A of Fig. 2 includes the twoway reinforcement B C together with means for stilfening the slab in the areas of the diagonals between equidistantly spaced columns. Instead of using heavier rods in the belt courses along the diagonals, the rods are of uniform cross section throughout, but the rods along thediagonals between the columns are grouped or crowded more closelyl together at B2 C2,y and in the diagonal areas between the columns the slab is made of greater depth so as to bring the steel lower down, thus resulting Vin an effective stiii'ening of the slab along the diagonal areas.' The rods B2 C2 extending across the columns are bent upwardly over the columns and additional rods H are used for taking care of the negative bending moment.

In the slab A of Figs. 3 and 5 the predominating element of a stiffer reinforce on the diagonals between the columns is disclosed, but` in this example of the invention the two-way reinforce afforded by the rods B C is sup emented by the use of groups 2 on the diagonals between the columns, the rods in each group B3 C3 being graduated in thickness toward the central diagonal line, the middle rods of the diagonal groupbeing the heavier and the rods decreasing from the middle rod B3 or C3 to the other rods of the two way reinforce B C. A mat or grill H is used in the upper chord of the slab and positioned over the column, and said Slab is increased in depth at b in the areas adjacent and over the column in order to take care of the negative bending moinentand the increased vertical shear.

rflue fiat slab shown in Fig. 6 of the drawings illustrates the two-way reinforcement comprising two crossin belt courses of rods B C extending paralle to the centre lines between the columns instead of diagonally. To secure the effect of increased stiffness on the Adiagonals between the columns I emp-loy short rods or bars B4 C4, one series B4 o-f which extends across the diagonal line between the columns D Gr whereas a second series C4 extends across the diagonal line between the other columns E F. These short rods B4 C4 are parallel to the rods B C respectively to constitute diagonal belts which add materially to the stiffness of the slab on the diagonalsbetween the columns, and said rods are positioned in the material of the slab below the neutral axis and in the tension chord thereo-f. Over the columns are the mats or grills H positioned in the upper chord of the slab.

As hereinbefore indicated, the two belt courses of rods crossing each other throughout the areaA of the slab provide spaces be tween the rods for the reception of tile blocks as shown in Fig. 7. The blocks I may be equalvin height to the depth of the slab so that the blocks cooperate with the rods B C and the concrete beams, but in the areas of the slab extending in the diagonale between t-he co-lumns Iprefer to use hea-vier rods B C as in Fig. 1 and to use tile blocks I, the height of which is less than that of the blocks I, thus enabling me to increase the thickness of the concrete material at c in the diagonal areasbetween the columns, whereby a strong slab reinforced at the lines of greatest stresses is obtained.

Although'l have described the flat slab as especially adapted for concrete buildings, it is to be understood that the monolithic structure is equally well adapted for foundations,.retaining walls, and the decks of shiIps, etc.

n the embodiment of the invention as heretofore described the columns are equidistantly spaced to the end that lines extending through the centers of said columns form the boundaries of squares, the stresses on the slab along the four boundary lines being equal and being taken care of by the two series of crossing rods, whereas the stresses on the longer diagonals between two columns' of adjacentpairs or couples are taken care rof by increasing the heaviness of the steel 9, thus resulting in an organization wherein the slab is subject to stresses on lines unequal in length in three respects; i. e. two short lines vbetween the four columns D F and E G as at 1 1 and 2 2; two longer lines between the columns D E and F Gr at 3 3 and 4-4, and two other still longer lines, one extending diagonally between columns D G, and the other extending diagonally between columns E F, the lines 1 1,

2 2, 3 3, 4 4 forming the boundaries of an oblong panel The steel in the oblong panels of Figs. 8 and 9 is distributed to perform the function of taking care of unit stresses to a substantially equal extent throughout the area of said oblong panels.

In Fig. 8, the crossing bars B C are arranged at angles other than right angles so that the spaces formed by the crossiner bars are of rhomboidal form, said bars B C extending diagonally across the boundary lines of the oblong panels supported by the spaced columns. Said bars B C stiffen the slab on the lines 1 1, 2 2, 3 3 and 4 4 so as to preclude fracture along the short lines 1 1 and 2 2 and on the longer lines 3 3 and 4 4 between the columns, the crossing of the rods B C at such angles as will produce rhomboidal figures tending to so group the rods along the two Sides unequal in length as to takecare of such stresses. In View of the fact that the diagonals between the columns in an oblong panel are considerably longer than eitherof the lines along the boundaries of such panels, I employ belts of heavier rods B5 C5 along the diagonals between columns D G and E F, said heavier rods B5 and C5 being parallel to the rods B C respectively and each belt course of heavier rods composing a part of the reinforcement afforded by one series of rods B or C. It should be stated that the heavier belt course B5 C5 between the columns are extended throughout the area of the slab so as to cross other similar rods of other panels in a manner for said heavier belt courses of rods B5 C5 to produce figures of rhomboidal shape, thus contributing to the stiffening of the slab throughout the area thereof by the economical use of steel.

The reinforce illustrated in Fig. 9 for an oblong slab embodies the two belt courses of rods B C crossing each other atv right vangles to result in square spaces adapted for the reception of tile blocks, the rods B being parallel to the longer lines 3 3 and 4 4.

at ltwo sides of the oblong whereasthe y rods C are'parallel to the shorterlines 1--1 ,andv

2-'2 at the two remaining sides;.of i the oblong., It is preferred, however, to use belt courses of heavier rods B9 between ,the

, columns D E and F G in order to takeY care of the stresses'along the longer -lines 3 -3 and 4 4. On the diagonals between the columns DV G and E F the steel is increased by the use of two belt courses of short rods,

. one belt course of short rods B7 being paralv tween columns D G and lel to rods B and 'extendin diagonally beother belt. course C7 of short rods-are arallel to rods C and extend diagonally etween columns D G and E F, the diagonal belt l courses of short rods B7 and CT taking care reinforcedv by steel rods as usual, or such of the stresses alon the lines of the longer diagonals between t e columns.

\ It is to be noted that the rods described are in the lower (tension) chord ofthe slab', below the neutralaxis thereof,V but I' utilize the grill or'mat G in the upper chord of the slab over each column for taking careof the increased vertical shearin the area of the slab adjacent the column.

, The columns may be composed of concrete columns may be composed of steel and the slabs supported thereon as disclosed in one of my prior ap lications.

Havin thus fiilly described the invention,v

what I c aim as new, and desire. to secure by rods of each belt course which are positioned along the diagonal lines between opposite columns of adjacent pairs of columns being increased in quantity with respect-to other rods of the same belt course extending in other areas of the slab, thereby producingv in the slab diagonally .to the columns distinctive areas the strength of which exceeds the strength in other areas of the slab.

2. A monolithic l'lat slab free from support along its several margins and sustained by columns the couples of which are spaced equidistantly embodying at least two belt courses of rods positioned in crossing relation and in the material of the slab substantially below the neutral axis and in the tension chord thereof andwith the individual rods of said belt courses running diagonally to the center lines extending between the pairs'of columns, the areas'of the slab extending 'diagonally between' oppositely strengt F, whereas the .placed columns- 'of adjacent pairs being vin-f.

creasingly stilfened and exceeding in the areas-extending between 'the columns on the center llineathereof as well as other portions of the slab'.

monolithic flat s1 b free yfrom sup.

ort along its several margins and sustained equidistantly embodying at least two belt vcourses of rods positioned in crossing rela- -tion and in the material-of the slabV substan- .tially below the lneutral axis'and in the tension chord thereof,the individual rods ofv each belt course being l.positioned diagonally to' the center lines between` the columns and the rods of one belt course crossing the'rod's of the other belt course,those rods in each belt course whichvextend between diagonally opposite ,columns 'of adjacent pairs exceeding vin cross' sectional area the 'rods fin the remaining area of the slab','whereby the slab isincreasingly stiffened in those areas which extend diagonally between oppositely placed columnsof adjacent pairs and which diagonally extending and increasingly stiened areas exceed in length the areas between the lcolumns on the center lines thereof.

4. A monolithic flat slab free from support along its several marginsv and sustained by columns vthe couples ofwhich 'are spaced equidstantly embodying atty least two belt courses of rods positioned in crossing relation and in the material of the slab substantially below the neutral axis and in the tension chord thereof,.th e individual rods of y columns thecou'ples of which are spaced each belt course being positioned diagonally tothe center line's between the columns and the rods of one belt course'erossing the rods of the other belt course, and hollow tilepositioned in the spaces boundedpby the crossing belt courses ofrods, therods extending between diagonally placed columns of adjacent pairs exceeding in cross sectional area the rods of the belt courses in the remainin area of the slab. f

5. A" monolithic flat slab free from support along its several margins and sustained by columns the-couples of which, are spaced equidistantly embodying at least two 4belt courses of rods positioned in crossing relation and in the material ofthe vslab substantially below the neutral axis and in the tension chordl thereof, the individual rods of each belt course being positioned diagonally to the center lines between the columns .and the rods of one belt course crossing the rods of the other belt course, the rods in the respective belt courses extending on the longer diagonal lines between opposite columns of adjacent pairs being composed of heavier material than the individual rods in the areas of the slab extending on the center lines between the columns.

6. A monolithic flat slab free from support along its several margins andsustained by columns the couples of which are spaced equidistantly embodying at least two belt courses of rods positioned in crossing relation and in the material of the slab substantially below the neutral axis and in the tension chord thereof, the individual rods of each belt course being positioned diagonally to the center lines between the columns and the rods of one belt course crossing the'rods of the other belt course. the rods in the respective belt courses extending on the longer diagonal lines between opposite columns of adjacentpairs being composed of heavier material than the individual rods in the areas of the slab extending on the center lines between the columns, and metallic mats positioned in the compression chord of the slab, one mat over each column, for taking cirl of the negative bending moment of the s a 7. A monolithic at slab supported solely on columns and initially stiffened by two belt courses of rods extending diagonally to the center lines between the columns and po sitioned in crossing relation to each other and in the material of the slab below the neutral axis thereof` the aggregate area of the rods being increased on the longer diagonal lines between diagonally opposite columns of adjacent pairs of columns.

8. A monolithic flat slab Supported solely on columns and initially stiifened by two belt courses of rods extending diagonally to the center lines between the columns and positioned in crossing relation to each other and in the material of the slab below the neutral axis thereof, the rods extending between diagonally opposite columns in adjacent couples of columns being heavier than the individual rods in the remaining area.

9. A monolithic flat slab supported solely on columns and initially stiffened by at least two belt courses of rods positioned in the material of the slab below the neutral axis thereof, and said rods of the belt courses extending diagonally to the center lines between couples of columns, the rods of one belt course crossing the rods of the other belt course to produce spaces rhomboidal in shape and the rods in each belt course which extend on the longer diagonal between diagonally placed columns of adjacent couples being heavier than the individual rods in the belt courses throughout the remainder of the slab, the heavier diagonal rods in one belt course crossing the similar heavier rods in the other belt course.

10. A monolithic flat slab supported solely on columns and provided with two belt courses of rods below the neutral axis of the slab and arranged for the rods of one'belt course to cross the rods of the other belt course throughout the area of the slab, and additional belt courses or short rods extending diagonally between the columns and positioned parallel to the rods of the first named belt courses` In testimony whereof I have hereunto signed my name this 29th day of May, 1918.

KARL R. SCHUSTER. 

